This invention relates to a blow torch having a dual gas supply, notably a combustible gas supply and a combustive gas supply, comprising a body having a first inlet connection for a first gas, a second inlet connection for a second gas, an outlet connection for supplying a nozzle or lance with a mixture of the two gases, a first duct extending between the first connection and the outlet connection and comprising a first tap, and a second duct extending between the second connection and the outlet connection and comprising a second tap, wherein each of the two taps comprises a core with a shoulder which is axially displaceable in a bore with a seating, for closing and opening the respective inlet connection.
The combustible gas may be propane, butane, acetylene or hydrogen, whilst the combustive gas is, for example, either oxygen or induced or compressed air. A blow torch of this kind may operate, for example at 0.5 bars for the combustible gas and, when oxygen is used, at 2 bars for the oxygen.
In general, dual gas supply blow torches have two spindle-type taps each having two separate controls. Such an arrangement necessitates delicate handling, particularly for ignition, as the tap for the fuel has to be opened first and then the tap for the combustive gas has to be turned on until the correct flame is obtained. If the overall flow rate needs to be modified, this has to be done cautiously so as to obtain both the desired overall flow rate and the correct proportions in the mixture.
In general, spindle-type taps also have the disadvantage of being difficult to regulate at low flow rates, and for this reason they are often provided with a needle valve in order to obtain fine adjustment; these needles are however fragile and substantially add to the bulk of the taps and to their production costs.
Generally, blow torches cannot be operated over a wide range of flow rates and a set of several blow torches is required in order to obtain flow rates ranging from a fraction of a liter per hour to several thousand liters per hour.
This invention relates to a blow torch which does not have these disadvantages and which provides a convenient means of balancing the proportions of the flow rates of fuel gas and combustive gas, with total control of the flow rate of the mixture, whilst giving a very wide range of flow rates ranging from a fraction of a liter to several thousand liters per hour.